booting back into the old 2.6.20 kernel from feisty (with acpi enabled) causes the acpi_listen messages to recur. So, it appears the 2.6.22 kernel fixed the issue.
booting back into the old 2.6.20 kernel from feisty (with acpi enabled) causes the acpi_listen messages to recur. So, it appears the 2.6.22 kernel fixed the issue.